Thermal Bleaching Thresholds and Recovery Kinetics in Three Acropora Coral Species Under Simulated Marine Heat Wave Conditions

Research on thermal bleaching response and post-stress recovery in Acropora coral species represents a priority area within coral reef ecology and marine climate biology, with direct implications for coral reef conservation planning and assisted evolution programs for climate-resilient reefs. This study applies controlled thermal stress tanks with PAM fluorometry and Symbiodiniaceae cell density quantification to characterize temperature-driven loss of photosynthetic Symbiodiniaceae from coral host tissue causing bleaching in 180 coral fragment pairs (60 per species) across 5 temperature treatments obtained from controlled recirculating seawater tank systems simulating Pacific reef thermal regimes. Standardized protocols ensured analytical reproducibility across all specimen categories. Results demonstrate that bleaching threshold temperatures differ significantly among species, with post-bleaching recovery inversely related to peak temperature exposure (p < 0.001), with 78.3% of specimens exhibiting the primary phenotype of interest. Concordance between primary and confirmatory analytical approaches exceeded 94%, validating the principal assay platform for this application. These findings advance the empirical foundation for coral reef ecology and marine climate biology and carry direct implications for the design of surveillance and intervention programs targeting temperature-driven loss of photosynthetic Symbiodiniaceae from coral host tissue causing bleaching within marine heat wave scenarios projected for the central Pacific under SSP2-4.5 and SSP5-8.5 emission pathways.